The invention presented here involves a nozzle head for the nebulization of liquids having different viscosities, suited to produce liquid particles having dimensions less than 1 xcexcm and to diffuse them in order to form a spray or an aerosol.
The invention presented here also relates to the nebulization device equipped with such a nozzle head.
Nebulization devices are designed to produce a fine particle spray for the purpose of purification of the atmosphere of place or premises such as premises that are open to the public. In this application, the spray formed can have properties of disinfection, deodorization, and at the same time, the substance sprayed can be a substance that has a smell in order to put a scent in the atmosphere.
Also, substances can be nebulized that have curative properties. Thus, it is known to use this type of device in medical fields such as the veterinary field notably for the treatment of respiratory canals, for vaccination of animals and for the disinfection of farming areas.
Also, these types of devices can also be used in the form of a spray for the formation of a mixture of combustive air with a fuel to supply boilers or even thermal engines.
Other areas of applications of this type of device are also known.
Regardless of the area of application of the device, the results and the efficiencies are even better since the spray is formed from particles having a size that is less than a micron, since the size of the particles is uniform and since the spray has a natural capacity to become diffuse and to become uniformly distributed in the volume in which it is introduced.
Known devices do not allow the known objectives indicated.
In fact, a size of particles that is not constant as well as in the end, a discharge of the large particles, which is manifest in a loss of liquid that can be very costly because of condensation on the surfaces, has been observed with these types of devices.
In order to avoid the discharge of large particles, certain nebulizers require at the outlet special geometric shapes in order to trap the large particles, prohibiting any axial exit of the spray, thus limiting the possibilities of integrating this type of device in assemblies for conveyance and distribution of the spray formed.
In addition, the particles formed with the devices of the prior art have a greater size such that the spray or the aerosol can be transported, without condensation, over great distances, for example, in an air conditioning network or in tubular elements having internal cross-sections on the order of a half-centimeter. These tubular elements can be used in order to transport the spray or the aerosol that is formed towards volumes several dozens of meters away from the nebulization device.
With most of these known devices, it is difficult to nebulize, with acceptable results, liquids having an extensive range of viscosity. In fact, these devices only function correctly for a specified range of viscosity that, moreover, turns out to be very narrow. In addition, this type of device does not offer the possibility for increasing or reducing the rated flow without changing the result.
Finally, the devices planned for the formation of particles having a size less than a micron function using very high air pressure.
The invention presented here has the purpose of solving the known problems mentioned by implementing a nozzle and a device for nebulization that is suitable for producing particles having a size less than 1 xcexcm and to release a spray or an aerosol that is made of particles having a uniform size constant in time that can be transported over relatively sizeable distances without any notable condensation effect in the transporting conduit.
Another purpose of the invention is to implement a nozzle head and a device for nebulization that are suitable to nebulize with the equivalent results, liquids having a very extensive range of viscosity and to do this at different flow rates.
Finally, a last purpose of the invention is to implement a nozzle head and a nebulization device suitable for making particles having a size that is less than a micron under low air pressure in a range of from 0.5 to 8 bars.
For this purpose, the nebulization nozzle head according to the invention is made of a body in which an open chamber for mixing and fractionation is formed, consisting of an outlet nozzle and in an opposite manner, at the base, a first nozzle behind which a supply hole is made in the body for gas under pressure, an input of the liquid to be nebulized being formed in the body in a manner communicating with the nozzle from the hole, and the input having been connected, by the intermediary of conduits, to a source of gas under pressure and to a reservoir of a liquid to be nebulized, the liquid being sucked into the mixing and fractionation chamber under the action of the partial vacuum created by the passage into it of the gas flow from the first nozzle to the outlet nozzle and being finely fractionated and mixed with the flow of gas under pressure under the effect of turbulences prevalent in this chamber, which has in front of the first nozzle, a spreading section, characterized in that:
the spreading section is formed by a surface of rotation,
the spreading section and the zone of the first hole situated immediately upstream from the spreading section are coaxial,
the introduction is radial in the direction of the flow of the air across the first nozzle,
a third nozzle is formed at the downstream end of the first hole at the level of its intersection with the input of the liquid,
the first and third nozzles are both in contact with the liquid input, are set apart from each other, and are formed by the sharp edges and can be aligned axially,
the type of the conical jet formed at the outlet of the nozzle head is conical and is made up of fine particles in the center and large particles at the periphery.
According to another characteristic of the invention, the liquid input is formed by at least one cylindrical radial hole terminated by a second formed nozzle and in the mixing and fractionation chamber and in the first hole (8), the geometrical longitudinal axis of symmetry from the zone of the second hole, located immediately upstream from the second nozzle is contained in the geometric plane containing the first nozzle which is defined by a sharp edge formed by the intersection of the spreading section with the upstream zone of the first hole.
the longitudinal axis of symmetry of the zone of the second hole located immediately upstream from the second nozzle is secant and perpendicular to the axis of symmetry of the spreading section.
Using these devices, at the output of the nozzle head, a conical jet is obtained which is made of fine particles having a size less than a micron, in a large number, and larger particles that are larger and thus heavier, in a reduced number.
The characteristics of the nozzle head make it so that a mixture of these particles is obtained that is non-homogeneous; the heaviest particles are located in the peripheral zone of the conical jet while the particles that are finer, and thus lighter, are located in the central zone.
Thus, already at the outlet of the nozzle head for nebulization and due to the characteristics of this nozzle head, the separation between the large particles to be extracted from the spray and the fine particles is done before the spray is formed.
In order to further improve this result, the spreading section extends evenly from the first nozzle to the outlet nozzle, i.e. over the entire length of the mixing and fractionation chamber, and it preferably has the shape of a truncated cone whose angle to the peak is made in a range from ten to ninety degrees. Excellent results have been obtained with an angle to the peak equal to sixty degrees. It goes without saying that these values are only given as a rough guide; the angle to the peak can be less than ten degrees or greater than ninety degrees.
The length of the chamber can be limited to a few millimeters, for example, to six millimeters, this length being sufficient in order to form a turbulence zone of sufficient size in order to ensure the separation of the particles.
It is noted that the turbulences are created essentially at the level of the two nozzles for the input of the liquid and compressed gas, due to the irregularity of the surface that is present at this level and due to the sharp edge that demarcates the nozzle from the compressed gas input.
Another factor that contributes to the creation of the turbulences is the imbalance of the jet formed, i.e. its offset relative to the axis of symmetry of the spreading section, this offset being due essentially to the presence of a unique nozzle for the liquid input.
In order to improve the flow rate while maintaining this imbalance, the invention, according to another of its characteristics, provides several second nozzles distributed in an irregular manner around the axis of symmetry of the mixing and fractionation chamber.
As a variation, a regular distribution can be provided, but with nozzles having different diameters.
According to another characteristic of the invention, the zone of the first hole, located immediately upstream from the first nozzle, and the zone of the second hole, located immediately upstream from the second nozzle, are both cylindrical. Moreover, the zone of the first hole, located immediately upstream from the first nozzle has a diameter that is smaller than the diameter of the zone of the second hole, located immediately upstream from the second nozzle.
Purely as a rough guide, these zones have diameters that are roughly equal to 400 xcexcm and to 800 xcexcm, respectively. It goes without saying that these values are only given purely as a rough guide, the respective values of the diameters of the two zones can be less than or greater than the values indicated.
By these relatively standard dimensions in the field of precision mechanics, it is thus possible to create nozzles fitted to create particles less than 1 xcexcm and this is done with the manufacturing tolerances standard in this field.
This is due to the fact that producing particles all having a size less than a micron at the output of the nebulization nozzle head had not been researched essentially with a view to efficiency and simplification of the creation, but on the contrary, unpredictably producing fine particles and coarse particles. The only requirement was that the fine particles that have dimensions less than a micron be sufficient in number in order to form a sufficiently dense spray in order to be used.
In order to greatly reduce the number of the large particles in the jet emitted by the nebulization nozzle head, according to another characteristic of the invention, above the outlet nozzle, at a distance from it, a deflector plane is mounted, where this deflector is perpendicular to the axis of symmetry of the chamber and centered relative to it. The deflector has a length and width greater than the diameter of the nozzle at the output and being notably designed to turn down the jet laterally towards the edge forming the nozzle at the outlet of the mixing chamber. This device makes it possible to create at this level, i.e. on the outlet nozzle, a fractionating of the large particles. In order to reinforce this result, the outlet nozzle is formed by a sharp edge. If desired, the deflector is designed to catch and deflect the large particles.
The size of the particles formed depends closely on the distance between the deflector and the nozzle of the outlet. As a guideline, this distance will be greater than 5 xcexcm and can be between 100 xcexcm and 5 mm. Depending on the case, the distance between the deflector and the outlet nozzle can be fixed or even adjustable in order to regulate the size of the particles emitted and to adapt the spraying nozzle head to the viscosity of the liquid to be nebulized. The distance between the deflector and the outlet nozzle determines the flow rate of the nebulization. In an unexpected manner, a low distance corresponds to a sizeable flow rate.
Excellent results have been obtained with a distance of 150 xcexcm.
Finally, the nebulization nozzle head, according to another embodiment form, can be provided with a hole planned for the vacuum extraction of residual flows, this second hole opening on the one hand, into the mixing and fractionation chamber and on the other hand, on one of the sides of the body of the nozzle head where it forms at this level a vacuum extraction opening of the residual flows of the liquid formed by the large particles.
The different characteristics of the nebulization nozzle head such as the ones that have just been listed allow nebulization with identical or at least, comparable, results for liquids having viscosities that are very far apart such as aqueous solutions and oils and this is done under a range of gas pressure and thus of flow rate, which as far as it is concerned is very extensive, for example, pressures from 0.5 bars to 8 bars.
In addition, the reduced length of the fractionation and mixing chamber from the nebulization nozzle head makes it possible to produce an effective response to the dimensional restrictions posed by the implantation in the devices of nebulization having a reduced size.
The nebulization device according to the invention is characterized essentially in that it is equipped with at least one nebulization nozzle head as described above.
This device, according to another characteristic, consists of a hollow body at the base of which and in which at least one nebulization nozzle head is mounted relative to on the one hand, a source of compressed gas by the intermediary of a conduit and on the other hand, with a reservoir of a liquid to be nebulized, mounted under the body, where the nebulization nozzle head, by its outlet nozzle, is in communication with an expansion chamber made in the body of the device, coaxial to the mixing and fractionation chamber of the nebulization nozzle head, the internal side of the chamber receiving the large particles emitted by the jet and catching them, so that they flow under the action of their weight on this side, towards the reservoir.
When the nozzle head is equipped with the deflector, the nebulized jet is caused to spin around in the expansion chamber. This is due to the sloped surface of the nozzle head whose main role is to conduct and direct this jet.
The jet of particles emitted by the nebulization nozzle head, as far as the peripheral zone of it is concerned, i.e. the one formed by the large particles, is oriented towards the inner side of the expansion chamber in a manner such that the large particles are caught by it.
According to another characteristic of the invention, the expansion chamber as opposed to the nebulization nozzle head, is limited by a transverse wall perpendicular to the geometric axis of the fractionation chamber, this wall contains in its center a hole that passes through the nebulization outlet. The height of this transverse wall relative to the spraying nozzle head as well as the diameter of hole passing through can vary as a function, for example, of the physical characteristics of the liquid to be sprayed.
According to yet another characteristic of the invention, the external side of the nebulization chamber, of the transverse wall, is convex and this wall consists of indentations on its periphery. This arrangement allows the flow towards the expansion chamber of any condensate formed above or on the transverse wall.
The inner side of the expansion chamber can be smooth, or even be equipped with one or more projections or hollows.
However, to the extent the configuration of the inner side of the chamber is smooth or has relief, it leads to a loss of a sizeable load.
From this loss of load, a drop in the speed of the progression of the spray of micro-particles results in the device, along with a risk of deposit and condensation, over time, of these micro-particles on the inner side of the body and as a consequence, a risk of driving the particles having a larger size into the jet of micro-particles.
In order to compensate for this disadvantage, according to another characteristic of the invention, the expansion chamber is extended by at least one acceleration zone of movement of the spray of particles in order to increase the speed of the spray and avoid any deposition of fine particles, the aforementioned zone being in contact with an outlet conduit of the spray or the aerosol formed.
The speed of the particles in the acceleration zone is sufficiently sizeable in order to prevent them from being caught and condensing against the walls of the hollow body.
In the preferred embodiment form, the acceleration zone of movement of the spray is in contact with the expansion chamber by a passage having a smaller cross-section than the cross-section of the chamber, this passage having a smaller cross-section can be formed, when the expansion chamber is limited by the transverse wall, by the hole passing through the wall.
This passage having a reduced cross section is favorable itself on the outlet, to emit a jet at an increased speed.
According to another embodiment form of the invention, the expansion chamber, as opposed to the nebulization nozzle head, contains a blockage wall and the wall of the reservoir, and above the maximum level of the liquid, is equipped with an outlet nozzle of the spray or aerosol. This embodiment form, which no longer provides the upper acceleration zone, enables the creation of a particularly compact device.
According to another characteristic of the invention, the body of the device, between the reservoir and the expansion chamber, is equipped with a transversal partition that carries the nebulization nozzle head. This partition, for a device equipped with an upper acceleration zone, ensures the air-tightedness between the expansion chamber and the zone of the reservoir located above the level of the liquid. This device prevents that under the effect of the pressure, the spray of particles is led towards the bottom and into the reservoir, which would weaken the efficiency of the device as a consequence.
For a device whose spray or aerosol outlet is guided into the wall of the reservoir, the partition will be equipped with a communication opening of the expansion chamber with the volume of the reservoir located above the level of the liquid.
According to another characteristic of the invention, the nebulization device is equipped with a mechanism for evacuation towards the reservoir the residual flows of the liquid formed by the large particles in the expansion chamber. This device prevents blocking of the expansion chamber by the flows.
According to another characteristic of the invention, the evacuation mechanism of the residual flows towards the reservoir passes through both sides of the partition. This mechanism, by its lower end, is located below the minimum level of liquid in the reservoir. This device, which provides a mechanism for the internal evacuation of the device, also leads to a better compactness of the device.
For a device whose expansion chamber is separated in an airtight manner from the zone of the reservoir located above the level of the liquid, the evacuation mechanism towards the reservoir, of the residual flows of liquid formed by the large particles, is made up of at least one tube engaged in a hole made in the transverse partition, where the partition and the tube ensure more separation between the volume of the reservoir located above the level of the liquid and the expansion chamber.
For a device whose expansion chamber is in communication with the zone of the reservoir located above the level of the liquid, the evacuation mechanism is made up of a blade engaged in the communication opening.
For a device equipped with a transverse partition ensuring the airtight separation between the expansion chamber and reservoir for the liquid to be nebulized, it is also possible to prevent the blocking of this chamber by the accumulation of residual flows using a nebulization nozzle head equipped with a vacuum extraction hole opening on one of the sides of the body of the nozzle head.